Closes gh-6978

Closes gh-7068

* pr/7081:
  Polish

Closes gh-7081

* pr/6991:
  Fix thymeleaf-layout-dialect.version in doc

Version 2.0.0 had serval bugs which broke compatibility to older
templates, so the guide should refer the fixed version instead.

Closes gh-6991

Closes gh-7051

Closes gh-7045

Update dependency management to exclude commons-logging and add
an enforcer rule to spring-boot-samples to try and prevent unwanted
commons-logging dependencies from sneaking back in again.

Closes gh-7067

* gh-7064:
  Prevent spring-session from pulling in commons-logging

Closes gh-7064

Closes gh-7063

Closes gh-7062

Closes gh-7061

Closes gh-7057

* pr/7030:
  Polish

Closes gh-7030

Closes gh-7042

Closes gh-6998

* pr/7025:
  Move Restarter in integration tests

Closes gh-7025

Closes gh-7026

Closes gh-7017

Closes gh-7007

* pr/7002:
  Exclude `META-INF/build-info.properties` from restart

Prior to this commit any application configured to write
`META-INF/build-info.properties` could trigger unexpected application
restarts. The problem is particularly prevalent when using Eclipse M2E in
combination with Maven's `spring-boot-maven-plugin` `build-info` goal
and Gradle's `springBoot` `buildInfo()`.

Closes gh-7002

See gh-6978

Remove setResolvePlaceholders() from PropertySourcesPropertyValues
and instead rely only on the constructor.

See gh-6964

Closes gh-6627

Closes gh-6956

Previously, when a Tomcat connector failed to start it was assumed that
the failure was due to the port being in use and a PortInUseException
was thrown. Unfortunately, this assumption doesn’t always hold true.
For example, a Tomcat connector will also fail to start when its using
SSL and the key store password is wrong. This could lead to incorrect
guidance from the PortInUseFailureAnalyzer indicating that a port clash
had occurred when, in fact, it was the SSL configuration that needed to
be corrected.

Unfortunately, Tomcat only tells us that the connector failed to start.
It doesn’t provide access to the exception that would allow us to
determine why it failed to start. This commit updates the embedded
Tomcat container to throw a ConnectorStartFailedException in the event
of a connector failing to start. A new failure analyser,
ConnectorStartFailureAnalyzer, has been introduced to analyse the new
exception and offer some more general guidance.

Closes gh-6896